Cancer pain has a major impact on quality of life and clinical treatment of patients. Oral cancer patients rate pain as their worst symptom. Effective treatment of cancer pain remains a critical, unmet goal in cancer research. The proposed study will provide a molecular rationale for the development of mechanism-based therapeutic treatments to reduce oral cancer pain, and cancer pain in general, and allow patients to regain their function. Cancer cells and cancer-associated stromal cells secrete a complex ensemble of bioactive factors into their surroundings to promote cancer growth. A subset of these molecules also sensitizes nociceptors on nearby primary afferent sensory neurons, creating crosstalk among nociception and cancer growth pathways. The proposed research is a targeted sampling and proteomic approach to characterize pain-producing proteases and peptides within the cancer microenvironment. The experimental advantage of our intraoperative microdialysis collection technique is the direct sampling of cancer-associated proteins and peptides in vivo. The nociceptive effect of molecules will be evaluated and confirmed using a well- established cancer pain mouse model. Secreted proteases are promising, yet largely unexploited drug targets for manipulating the levels of pain-producing peptides. We hypothesize that selective inhibition of specific proteases will decrease levels of nociceptive peptides in the cancer environment and relieve cancer-associated pain. The data generated from the proposed studies will provide the molecular basis for an entirely new perspective with which to understand and treat cancer pain.